Apparatus for producing corrugations on screens of fully-filled cables

ABSTRACT

Corrugating apparatus for producing circumferentially extending sealing corrugations in the electrostatic or electromagnetic screen of a fully-filled telephone cable, the apparatus comprising an even number of rollers having concave faces to fit partly around the cable screen and disposed with respect to each other in the circumferential direction of the cable to define a circular cable receiving cavity. The rollers have their planes of rotation parallel to the longitudinal axis of the cable and have mating gear teeth at their sides so that the rollers rotate in synchronism. Each roller has a plurality of axially extending, spaced, concave ridges on its concave face, and at its ends, each ridge of one roller overlaps ridges of adjacent rollers so that, effectively, the combination of the overlapping ridges form a single annular ridge extending circumferentially of the screen and having a diameter substantially equal to the diameter of the cable core within the screen. The peripheries of the rollers, and hence, the ridges, are adjustably spring biased toward the cable screen.

United States Patent [19] Ferrentino Mar. 18, 1975 I APPARATUS FOR PRODUCING CORRUGATIONS ON SCREENS OF FULLY-FILLED CABLES [75] Inventor: Antonio Ferrentino, Monza, Italy [73] Assignee: lndustrie Pirelli Societa per Azioni,

Milan, Italy [22] Filed: May 1, 1974 [21] Appl. No.: 465,828

[52] US. Cl. 72/194, 72/224 [51] Int. Cl B21d 15/06 [58] Field of Search 72/194, 198, 224

[56] References Cited UNITED STATES PATENTS 2,614,607 10/1952 Klein, 72/l94 3,641,799 2/1972 Wildt 72/l98 FOREIGN PATENTS OR APPLICATIONS l82.939 8/1955 Austria 72/194 851,79] 10/1952 Germany 72/194 Primary Emminer-Lowell A. Larson Attorney, Agent, or Firm-Brooks Haidt & Haffner [57] ABSTRACT Corrugating apparatus for producing circumferentially extending sealing corrugations in the electrostatic or electromagnetic screen of a fully-filled telephone cable, the apparatus comprising an even number of rollers having concave faces to fit partly around the cable screen and disposed with respect to each other in the circumferential direction of the cable to define a circular cable receiving cavity. The rollers have their planes of rotation parallel to the longitudinal axis of the cable and havemating gear teeth at their sides so that the rollers rotate in synchronism. Each roller has a plurality of axially extending, spaced, concave ridges on its concave face, and at its ends, each ridge of one roller overlaps ridges of adjacent rollers so that, effectively, the combination of the overlapping ridges form a single annular ridge extending circumferentially of the screen and having a diameter substantially equal to the diameter of the cable core within the screen. The peripheries of the rollers, and hence, the ridges, are adjustably spring biased toward the cable screen.

14 Claims, 8 Drawing Figures PATENTEUHAR 1 8M5 SHEET 3 BF 5 /QN in,

Q NN ON SCREENS OF FULLY-FILLED CABLES I The present invention relates to apparatus for producing circumferential corrugations able to constitute a hydraulic barrier on normally smooth metallic screens of the longitudinal type formed by tapes clad with thermoplastic material, called composite tapes, and used in fully-filled telephone cables for an electrostatic and/or electromagnetic screening function.

As is known to those skilled in this field, the corrugations on said types of screens, in fully-filled cables, have the purpose of bringing, in circumferential zones, the inner surface of the screen into contact with the wrappings which cover the core in order to create a hydraulic barrier against the flow of water or other liquids which may penetrate below-the screen in consequence of accidental leaks.

The present invention has, as one object, the provision of apparatus able to produce a plurality of circumferentially arranged segmental corrugations or indentations which in their whole can be compared, in crosssection, to an annular continuous trough, devoid of corners, which might keep the screen separated from the wrappings.

Cables having this feature are described in my copending application Ser. No. 466,177 filed May 2, 1974, and entitled FULLY-FILLED TELEPHONE CABLE WITH IMPROVED SCREEN, corresponding to Italian application No. 24,440A/73.

More generally speaking, the apparatus according to the present invention permits the obtaining of a plurality of segmental corrugations which, together, ensure a continuous circumferential contact of the inner surface of the screen with the wrappings.

More specifically, the main object of the invention is apparatus for producing circumferential sealing corrugations or indentations on the screen of a fullyfilled cable, characterized in that it comprises a plurality, even in number, of grooved rollers, identical to and synchronized with each other. The rollers are arranged as a crown around a circular cavity having a diameter equal to the maximum diameter of the screen of the fullyfilled cable to be corrugated with said apparatus, each roller being provided, in its groove, with one or more transverse ridges. Each ridge of one roller is adjacent to the ridges of the two adjacent rollers at portions of its free ends, each ridge being therefore offset with respect to the ridges of the preceding and subsequent rollers in the crown, and the ridges being aligned in the same circumferential plane.

The present invention will be better understood from the following detailed description of a preferred embodiment of the invention, which description should be considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic, front elevation view of the head portion of one embodiment of the apparatus of the invention;

FIG. 2 is a detailed, diagrammatic, perspective view of two of the rollers of the head portion shown in FIG.

FIG. 3 represents a projection on the plane of the working surfaces of three rollers of the head portion shown in FIG. 1;

FIG. 4 is a longitudinal section of a portion of the embodiment of the invention which includes the rollers shown in the preceding figures;

FIG. 5 is a front, elevation view, partly in' crosssection, of the preferred embodiment of the mounting of the head portion shown in the preceding figures;

FIG. 6 is a longitudinal section of a portion of a modified embodiment of the apparatus of the invention;

FIG. 7 is a longitudinal section of a portion of a modifled embodiment of the apparatus of the invention; and

FIG. 8 is an exploded, perspective view of two parts of the apparatus of the invention.

As mentioned hereinbefore, the purpose of the apparatus is to provide corrugations-or indentations in the screen of a telephonecable as illustrated and described in said copending application to'which reference is made for a better understanding of the purpose of the apparatus. 7

The apparatus of the invention is provided with a head 10 comprising an even number group or plurality, even in number, of peripherally grooved rollers, for example, six rollers R, R (FIG. 1) which, preferably, are identical to each other and are connected so that they rotate in synchronism. The rollers R, R are arranged as a crown around a cylindrical opening 11, the diameter of which is at least equal to the diameter of the screen 12 of the fully-filled cable 13 to be corru gated. In any event, the diameter of the opening 11 is at least equal to the maximum diameter of the screen 12 of a fully-filled cable which is to be corrugated with said rollers R, R

The expression arranged as a crown means that the axes of rotation of the rollers R, R define an imaginary regular polygon concentric with said opening 11 and having a number of sides corresponding to the number of rollers R, R,,. It will also be noted that when the rollers R, R are so arranged, their planes of rotation extend radially outwardly from a common point which is the center of the opening 11.

In the illustratedembodiment, the rollers R, R are synchronized with one another by means of bevel gear teeth of equal number, pitch, etc. provided at the borders of the grooveof each roller.

For the sake of simplicity, only two of the six rollers will be described in detail hereinafter. Reference is made to FIG. 2 which shows two rollers R, and R having the teeth I, and I, thereon.

The peripheral face of each roller, R, R has a groove, S, S therein which, when viewed in crosssection, is arcuate and concave. The surfaces of the grooves 8,, S of the rollers R,, R respectively, are provided at both of their respective borders with the bevel gear teeth I,, I", and 1' I,;, having an equal modulus. The bevel gear teeth of a roller engage the corresponding teeth of the preceding roller in the crown, while the other gear teeth at the opposite side thereof engage the corresponding gear teeth of the subsequent roller in the crown. In FIG. 2, it is apparent how the gear teeth I", of the roller R, engage with the gear teeth 1' of the roller R The groove of each roller is provided with one or more transverse ridges, e.g., ridges A, and A the term transverse ridges meaning ridges extending from one border or side face of the roller to the other. Each transverse ridge has a height and a thickness appropriately sized as a function of the material forming the screen 12 to be corrugated. The radially outward face of each ridge, A, A when viewed in cross-section, is arcuate and concave and has a radius substantially equal to the radius of the core of the cable 13 so that during the operation of the apparatus, the screen 12 is pressed against the core by the ridges.

Each ridge of a roller is adjacent to, and overlaps, the ridges of the two adjacent rollers for portions of its free ends, so that each ridge is offset with respect to the ridges of the preceding and subsequent rollers in the crown, and the latter are aligned in the same circumferential plane. This appears more clearly from FIGS. 2 and 3 wherein the ridges of the various rollers are mutually arranged in sucha relationship that ridge A, extends from side F of the tooth D, of the gear teeth to side F", of the corresponding tooth D", of the-other gearteeth I",, of the roller R The ridges of the preceding and subsequent rollers R and R, extend respectively from the side F", of the tooth D", in contact with the side F of the first tooth D, and from the side F' of the tooth D' in contact with the other side F",,- of the tooth D" Each roller is similarly constructed and is similarly related to the adjacent rollers, and the ridges A, A form, with their at least partial alignment, a solid figure which, with good approximation, can be defined as annular.

Each of the rollers R, R is rotatablycarried about its own axis aa (see FIG. 2) by a square-shaped fork 14 (FIG. 4) pivotally mounted on a small shaft 36 carried by ears 17 extending from an annular support 18. The fork 14 is provided with an arm 16 which engages a tooth 46 on a hollow tie rod 19.

An annular support 18 slidably engages one end of the hollow tie rod 19 having an inner diameter greater than the maximum outer diameter of the cable to be corrugated by the apparatus. The hollow tie rod 19 protrudes outwardly, with respect to the annular support 18, and has a portion provided with a first flange 20 comprising seats for receiving lugs 44 and 45 (FIGVS) of the arm 16 of each fork 14 for the rollers R, R

The back portion 21 of the support 18 is provided with a first cylindrical extension 22, co-axial with respect to the hollow tie rod 19 and defining a first housing 23 intended to house an elastic element, in the particular case illustrated, a helical spring 24 which applies the working pressure to the roller supported by the fork l4, e.g., roller R,, R etc.

The outer surface of the hollow tie rod 19 is threaded on its outer surface at the end opposite to the flange 20, and a ring nut 25 having mating threads and provided with a radial flange 26 engages the threaded portion of the rod 19. The radial flange 26 engages the end of the spring 24 opposite from the end thereof which engages the support 18. By turning, and thereby adjusting the position of, the ring nut 25, it is possible to increase the compression of the spring 24. When the compression of the spring is increased, the pressure of the rollers and, consequently, that of the ridges A,, A on the screen 12 of the cable is increased.

The flange 26 of the ring nut 25 is also provided with a cylindrical extension 27 coaxial with the first extension 22 and partially covering the outer surface 47 of the extension 22. Said outer surface 47 is provided with a graduated scale marking which, by suitable means, for example, the edge of the cylindrical extension 27 referred to, permits the load on the spring caused by the ring nut 25 to be read directly.

The cylindrical opening 11 defined by the rollers R, R is suitable for cables 13 having a screen 12 with an outer diameter with a predetermined range of values. If it is wished to corrugate a fully-filled cable 13 having a diameter above or below the predetermined range of values which can be operated on bya set of the rollers R, R it is necessary to replace said rollers with a set appropriate for the range of diameters of the screen of the fully-filled cable to be corrugated.

FIGS. 5 and 6 illustrate an embodiment of the mounting of the rollers R, R, which permits rapid changing of allthe rollers R, R in order to adapt said head 10 to a pre-establi'shed different range of outer diameters of the screen 12 of a fully-filled cable 13 to be corrugated.

Each roller R, R is connected, through the free end of its own fork 14, to the annular support 18a by means of an annular element 28. Said annular element 28 is provided with means which permits its prompt application and removal frontally and co-axially with respect to the annular support 180. As shown in FIGS. 5 and 6, the element 28 has radial extensions 29, directed radially outwardly, on its circumferences. Said radial extensions 29 are preferably, but not necessarily, circumferentially equi-distant.

The support is provided on its front part with a cylindrical, hollow extension 30, which defines a seat 31, intended to receive said annular element 28. The cylindrical, hollow extension 30 is provided at its free end with a flange 32 oriented radially inwardly and having an inner diameter equal to, or slightly greater than, that of the annular element 28 at the base of the extensions 29. 1

The flange 32 is provided with notches 33 having the same configuration, but a size slightly greater than that of the radial extensions 29. the notches 33 are arranged on the circumference in the same spacing as said radial extensions 29. Therefore, the annular element 28 can be inserted in the same manner as with a bayonet-joint, i.e., the element 28 is moved axially with the extensions 29 aligned with the notches 33 and is rotated around its axis to lock or unlock it, the locked position being shown in FIG. 5.

As stated hereinbefore, the rollers R, R of a given size mounted on the annular element 28 are suitable for a pre-established range of external diameters of screens 12 for fully-filled cables. If it is desired to apply rollers R, R intended for a certain range, the unit constituted'by the rollers R, R and by the annular element 28 is simply positioned in front of the flange 32 in such a way that the radial extensions 29 coincide with the notches 33, and the annular element 28 is pushed axially into the cavity 31. Then, the unit is rotated in such a way that the radial extensions 29 are covered by the walls of the flange 32 between the notches 33. The opposite operation permits the disengagement of the unit formed by the rollers R, R and by the annular element 28 from the support 18a.

FIG. 7 illustrates an alternative embodiment of the apparatus illustrated in FIG. 6. In said FIG. 7, the annular element 28b is provided with at least a first opening 34 adjacent the upper end of an arm 15 of each fork 14 for receiving an elastic element 35 which urges the respective roller R, toward the screen 12 and around the fulcrum 36.

The roller biasing arrangement which has been described with reference to FIG. 7 can, of course, be applied also to the embodiments in FIGS. 4 and 6 and to the embodiments described hereinafter.

In FIG. 7, a second opening 37, co-axial with the hollow tie rod 19, is-provided between the inner part of the annular support 18c and the outer part or surface of the hollow tie rod 19. Said opening 37 receives a third elastic element, for example, a helical spring 38, which, at its free end engages the back portion 39 of an annular element 40 slidably mounted on the hollow tie rod 19 and engaging at its front part 41, the free end of the arm 16.

Preferably, the arm 16, integral with the fork 14, is shaped as shown in FIG. 8, namely, its free end directed towards the back portion 42 of the flange 20, and is provided with the lug 45 directed axially. In turn, said the filling material as described in said application.

lug 45 is constituted by two teeth 43, .44 spaced apart I for a distance 8, equal to or greater than 5 of a corresponding extension 46, which protrudes radially outwardly from the flange 20. The latter will, therefore, be provided with as many radial extensions 46 as are the rollers of the head 10.

When the unit formed by the rollers R, R and by the annular element 28b is assembled, as stated hereinbefore, in the cavity 31 of the annular support 18c, the teeth 43, 44 of the lug 45 take a position astride the extension 46 and are retained in said position, during the operation of the apparatus, by the ring 40 because of the action of the spring 38.

Although the head of the above-described corrugating apparatus is provided with only six rollers, it is obvious that said rollers can be provided in a different number, but always more than four. Moreover, more than one corrugating head can be provided on a corrugating apparatus.

Furthermore, a corrugating apparatus according to the invention and comprising an interchangeable unit formed by the rollers R, R and by an annular element 28, 28a or 28b, can be provided with all the auxiliary elastic elements 35, 38 or with one or none of them, according to the requirements encountered.

Another detail of construction which can be varied is the shape of the ridges A, A

Assuming that a fully-filled cable 13 is to be corrugated, a corrugating apparatus will then be used in which the rollers R, R define with their groove trough a cavity whose diameter is at least equal to the diameter of the cable of maximum diameter which is to be corrugated.

The fully-filled cable 13 with the screen 12 is inserted in the hollow tie rod 19 (FIG. 4) and is pulled in the direction of the arrow F while the support 18, 18a or 1817 is held in a fixed position. Said fully-filled cable 13, without a protective sheath but provided with the screen 12, passes through the cavity 11 defined by the rollers R, R arranged as a crown (FIG. 1) and causes, by reason of engagement with the rollers R, R the rotation of each of said rollers about its own axis.

The plurality of ridges A, A which define a cavity having a diameter smaller than the normal outer diameter of the cable screen by an amount at least equal-to the height of the hollow space existing between the screen 12 and the wrappin gs of the core, impress on the screen corresponding corrugations at a constant spacmg.

Said corrugations, although they are defined by a plurality of annular segments, can be considered as substantially circumferential in the whole, since each an- Although a preferred embodiment of the present invention has been described and illustrated, it will be understood by those skilled in the art that various modifications may be made without departing from the principles of the invention.

What is claimed is:

1. In apparatus for producing circumferential sealing corrugations on the screen of a fully-filled cylindrical cable having a core with said screen therearound, a plurality of rotatable, similar rollers, even in number and at least six in number, means supporting said rollers side-by-side and as a crown around a circle having a diameter equal to the maximum diameter of the screen to be corrugated and with the planes of rotation thereof perpendicular to the plane of said circle, each of said rollers having radially extending side faces with a peripheral groove therebetween and having at least one ridge extending transversely of said groove and from one said side face to the other, said ridge having an arcuate, concave, radially outward face which is radially outward of said groove, said rollers being mounted with each ridge of one roller overlapping at its end portions the end portions of the ridges on rollers at opposite sides of said one roller, whereby ridges of alternate rollers lie substantially in a plane substantially parallel to said plane of said circle, and means interconnecting said rollers for restricting said rollers to rotation in synchronism with each other.

2. In apparatus for corrugating the screen of a cylindrical cable having a central core surrounded by said screen, a plurality of rotatable rollers, even in number and at least equal to six in number, means supporting said rollers in side-by-side relation with their planes of rotation extending radially outwardly from a common point each of said rollers having radially extending side faces and having a concave, grooved peripheral face intermediate said side faces, each roller being mounted with its peripheral face adjacent a circle drawn about said common point and having a diameter equal to the diameter of said screen and each of said rollers having at least one ridge on its peripheral face extending radially outwardly and transversely of said peripheral face from one side face to the other side face thereof, the radially outward face of said ridge being arcuate and concave and having a radius substantially equal to the radius of said core, said rollers also being mounted with the ridge of one roller overlapping at its end edge portions the end edge portions of ridges on adjacent rollers, whereby ridges on alternate rollers lie substantially in a plane parallel to the plane of said circle, and means interconnecting said rollers for restricting rotation thereof to rotation in synchronism with each other.

3. Apparatus as set forth in claim 2, wherein said means for interconnecting said rollers comprises teeth at opposite side faces of each roller, the teeth of each roller meshing with the adjacent teeth of the rollers adjacent thereto.

4. Apparatus as set forth in claim 3, wherein said ridge on a roller extends from a side of a tooth at one side face of the roller to the corresponding side of a corresponding tooth at the opposite side face of said lastmentioned roller. v

5. Apparatus as set forth in claim 2, wherein said supporting means comprisesa hollow tie rod having an internal diameter greater than the diameter of said cable mounted concentrically with said circle, an annular support mounted on and extending around said tie rod, and a plurality of forks, one for each roller, pivotally mounted at one end thereof on a surface of said support, each roller being rotatably mounted on a said fork at a position thereon spaced from said end thereof.

6. Apparatus as set forth in claim 5, wherein said tie rod has a flange thereon extending radially outwardly and adjacent a side of said support, said flange having a plurality of circumferentially spaced seats at least equal in number to the number of said forks, each said fork has an extension thereon extending from said pivotally mounted end to and engaging one of said seats, and said support is slidably mounted on said tie rod for movement axially thereof, and further comprising spring means acting between said tie rod and said support for urging said support toward said flange.

7. Apparatus as set forth in claim 6, wherein said tie rod has a threaded exterior portion spaced from said flange and on the opposite side of said support from said flange and said spring means is a helical spring having an end thereof against said support on the side thereof opposite from said flange and a ring nut in threaded engagement with said threaded portion and engaging the opposite end of said spring.

8. Apparatus as set forth in claim 7, wherein said extension has a forked end engageable with said seats and said seats comprise a plurality of radial extensions on said flange which are receivable by said forked end.

9. Apparatus as set forth in claim 6, further comprising spring means between said support and each of said forks for urging said forks, and the rollers carried thereby, radially inwardly.

10. Apparatus as set forth in claim prising spring means between said support and each extension of said forks for urging said forks, and the rollers carried thereby, radially outwardly.

11. Apparatus as set forth in claim l0,'wherein said spring means is a ring slidably mounted on said tie rod and'engaging each extension and a helical spring intermediate said ring and said support with one end thereof against said ring and with the other end thereof against said support.

12. Apparatus as set forth in claim 5, further comprising spring means between said support and each of said forks for urging said forks, and the rollers carried thereby, radially inwardly.

13. Apparatus as set forth in claim 5, wherein said support comprises first and second annular members, said forks being mounted on said second annular member, and said first annular member having a rim extending around the periphery of said second annular member.

14. Apparatus as set forth in claim 13, wherein said second annular member has a central opening therein of a size permitting removal of said second annular member over said flange and has radially outwardly extending, circumferentially spaced extensions and wherein said rim has a radially inwardly extending flange of an inner diameter less than the outer diameter of said extensions, said last-mentioned flange having notches therein corresponding inspacing to the spacing of said extensions and permitting said extensions to pass therethrough when said extensions have a position in which they are aligned with said notches in the direction of the axes of said annular members, said flange preventing the passage of said extensions when said extensions have a different position.

9, further com- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,871,207 Dated March 18, 1975 Inventor) Antonio Ferrentlno It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Insert:

Identifier [301' Foreign Application Priority Data May 23, 1973 Italy ........2444lA/73 Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Conunissioner of Patents and Trademarks Attesting Officer 1 FORM PO-105O (10-69) USCOM'WDC 6O376 p69 w u s covsmmnn rnmnuc ornc: as! o-ass-na 

1. In apparatus for producing circumferential sealing corrugations on the screen of a fully-filled cylindrical cable having a core with said screen therearound, a plurality of rotatable, similar rollers, even in number and at least six in number, means supporting said rollers side-by-side and as a crown around a circle having a diameter equal to the maximum diameter of the screen to be corrugated and with the planes of rotation thereof perpendicular to the plane of said circle, each of said rollers having radially extending side faces with a peripheral groove therebetween and having at least one ridge extending transversely of said groove and from one said side face to the other, said ridge having an arcuate, concave, radially outward face which is radially outward of said groove, said rollers being mounted with each ridge of one roller overlapping at its end portions the end portions of the ridges on rollers at opposite sides of said one roller, whereby ridges of alternate rollers lie substantially in a plane substantially parallel to said plane of said circle, and means interconnecting said rollers for restricting said rollers to rotation in synchronism with each other.
 2. In apparatus for corrugating the screen of a cylindrical cable having a central core surrounded by said screen, a plurality of rotatable rollers, even in number and at least equal to six in number, means supporting said rollers in side-by-side relation with their planes of rotation extending radially outwardly from a common point, each of said rollers having radially extending side faces and having a concave, grooved peripheral face intermediate said side faces, each roller being mounted with its peripheral face adjacent a circle drawn about said common point and having a diameter equal to the diameter of said screen and each of said rollers having at least one ridge on its peripheral face extending radially outwardly and transversely of said peripheral face from one side face to the other side face thereof, the radially outward face of said ridge being arcuate and concave and having a radius substantially equal to the radius of said core, said rollers also being mounted with the ridge of one roller overlapping at its end edge portions the end edge portions of ridges on adjacent rollers, whereby ridges on alternate rollers lie substantially in a plane parallel to the plane of said circle, and means interconnecting said rollers for restricting rotation thereof to rotation in synchronism with each other.
 3. Apparatus as set forth in claim 2, wherein said means for interconnecting said rollers comprises teeth at opposite side faces of each roller, the teeth of each roller meshing with the adjacent teeth of the rollers adjacent thereto.
 4. Apparatus as set forth in claim 3, wherein said ridge on a roller extends from a side of a tooth at one side face of the roller to the corresponding side of a corresponding tooth at the opposite side face of said lastmentioned roller.
 5. Apparatus as set forth in claim 2, wherein said supporting means comprises a hollow tie rod having an internal diameter greater than the diameter of said cable mounted concentrically with said circle, an annular support mounted on and extending around said tie rod, and a plurality of forks, one for each roller, pivotally mounted at one end thereof on a surface of said support, each roller being rotatably mounted on a said fork at a position thereon spaced from said end thereof.
 6. Apparatus as set forth in claim 5, wherein said tie rod has a flange thereon extending radially outWardly and adjacent a side of said support, said flange having a plurality of circumferentially spaced seats at least equal in number to the number of said forks, each said fork has an extension thereon extending from said pivotally mounted end to and engaging one of said seats, and said support is slidably mounted on said tie rod for movement axially thereof, and further comprising spring means acting between said tie rod and said support for urging said support toward said flange.
 7. Apparatus as set forth in claim 6, wherein said tie rod has a threaded exterior portion spaced from said flange and on the opposite side of said support from said flange and said spring means is a helical spring having an end thereof against said support on the side thereof opposite from said flange and a ring nut in threaded engagement with said threaded portion and engaging the opposite end of said spring.
 8. Apparatus as set forth in claim 7, wherein said extension has a forked end engageable with said seats and said seats comprise a plurality of radial extensions on said flange which are receivable by said forked end.
 9. Apparatus as set forth in claim 6, further comprising spring means between said support and each of said forks for urging said forks, and the rollers carried thereby, radially inwardly.
 10. Apparatus as set forth in claim 9, further comprising spring means between said support and each extension of said forks for urging said forks, and the rollers carried thereby, radially outwardly.
 11. Apparatus as set forth in claim 10, wherein said spring means is a ring slidably mounted on said tie rod and engaging each extension and a helical spring intermediate said ring and said support with one end thereof against said ring and with the other end thereof against said support.
 12. Apparatus as set forth in claim 5, further comprising spring means between said support and each of said forks for urging said forks, and the rollers carried thereby, radially inwardly.
 13. Apparatus as set forth in claim 5, wherein said support comprises first and second annular members, said forks being mounted on said second annular member, and said first annular member having a rim extending around the periphery of said second annular member.
 14. Apparatus as set forth in claim 13, wherein said second annular member has a central opening therein of a size permitting removal of said second annular member over said flange and has radially outwardly extending, circumferentially spaced extensions and wherein said rim has a radially inwardly extending flange of an inner diameter less than the outer diameter of said extensions, said last-mentioned flange having notches therein corresponding in spacing to the spacing of said extensions and permitting said extensions to pass therethrough when said extensions have a position in which they are aligned with said notches in the direction of the axes of said annular members, said flange preventing the passage of said extensions when said extensions have a different position. 